(CNN) -- Prince William has spoken in depth publicly for the first time about death of his mother, Diana, Princess of Wales, 12 years ago, saying "mummy" is now a hollow word "evoking only memories."

Diana, Princess of Wales, died in a Paris car crash 12 years ago.

Prince William was only 15 and his brother Prince Harry 12 when Diana died in a Paris car crash along with Dodi Fayed in 1997.

The Prince made the comment Thursday during a speech to mark his new role as patron of Britain's Child Bereavement Charity -- a group his mother was once involved with.

The British Press Association reported that he told the launch of the charity's Mother's Day campaign: "My mother Diana was present at your launch 15 years ago, and I am incredibly proud to be able to continue her support for your fantastic charity, by becoming your royal patron.

"What my mother recognized then -- and what I understand now -- is that losing a close family member is one of the hardest experiences that anyone can ever endure.